Melt intrusion as a trigger for lithospheric foundering and the eruption of the Siberian flood basalts

Abstract

Any viable model of the Siberian flood basalt (SFB) eruption must provide for a massive pulse of magma, initially erupted below sea level. We propose as a triggering mechanism a limited precursory melt that intrudes and heats the mantle lithosphere, lowering its viscosity, and increasing its density as the melt freezes into eclogite. This warm, dense mantle lithosphere is then removed via a Rayleigh‐Taylor instability that creates surface subsidence. Removal of the mantle lithosphere lengthens the melting column, and the melt volume of the SFB can be produced in less than a million years. The model is permissive of the existing geologic data for the SFB, which rule out a traditional hot, deep mantle plume. Numerical models demonstrate that the ability of a mantle upwelling to remove lithosphere is dependent primarily upon the lithospheric rheology, not on the temperature or size of the upwelling.